The electric utility industry is seeking to correct existing ground or aerial transmission line clearance problems or increase the capacity of existing electric power transmission lines while maintaining the required ground clearance through upgrades to the current transmission infrastructure. Utilities have increased the loads carried by power lines to meet ever-increasing demand during peak loading conditions, such as, for example, those that occur with seasonal heating and air-conditioning loads. This increased line loading creates additional transmission line sag resulting in wire to ground and or object clearance violations. Also, utilities are faced with increasing wire/hardware ground and aerial clearance requirements brought on by erection of nearby structures and/or new codes and/or regulations, which impose new clearance requirements on existing tower line infrastructure.
To mitigate changing (increasing) line height requirements, some utilities in the industry have addressed the need to increase tower heights by adding a tower extension (insert) to the body of the tower generally located at the waist or mid-portion of the tower. The tower extension increases the tower height and eliminates the need to replace or change out the existing lattice structure or string new cables. The current method involves splitting the tower at its connection location and using a crane to lift the top section of the tower to the desired height so the extension can be placed within the open section of the tower. The extension is then attached to both the top and bottom section of the existing tower. When tower extensions are performed in this manner the power lines, communication lines, and other equipment carried must be de-energized and disconnected and reconnected to the structure once the extension is put in place. This results in considerable downtime of the entire power transmission and communication system. Moreover, this procedure can only be conducted on structures which have near perfectly balanced weight loads so the top suspended section of the tower can be hoisted without rotation. If the weight loads are unbalanced the tower height cannot be increased in this manner.